Re: [Qemu-devel] [PATCH v3 4/6] block/nvme: add support for image creation

[Max Reitz <mreitz@redhat.com>]

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On 03.07.19 17:59, Maxim Levitsky wrote:
> Tesed on a nvme device like that:
> 
> # create preallocated qcow2 image
> $ qemu-img create -f qcow2 nvme://0000:06:00.0/1 10G -o preallocation=metadata
> Formatting 'nvme://0000:06:00.0/1', fmt=qcow2 size=10737418240 cluster_size=65536 preallocation=metadata lazy_refcounts=off refcount_bits=16
> 
> # create an empty qcow2 image
> $ qemu-img create -f qcow2 nvme://0000:06:00.0/1 10G -o preallocation=off
> Formatting 'nvme://0000:06:00.0/1', fmt=qcow2 size=10737418240 cluster_size=65536 preallocation=off lazy_refcounts=off refcount_bits=16
> 
> Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
> ---
>  block/nvme.c | 108 +++++++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 108 insertions(+)

Hm.  I’m not quite sure I like this, because this is not image creation.

What we need is a general interface for formatting existing files.  I
mean, we have that in QMP (blockdev-create), but the problem is that
this doesn’t really translate to qemu-img create.

I wonder whether it’s best to hack something up that makes
bdrv_create_file() a no-op, or whether we should expose blockdev-create
over qemu-img.  I’ll see how difficult the latter is, it sounds fun
(famous last words).

Max


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